The present invention relates to temperature measurement systems and, more particularly, to techniques for reducing transient error in temperature sensors to improve response time.
In the prior art there are known a variety of temperature sensing systems which use a temperature sensing element to provide an outlet voltage which is a representation of the temperature of the environment in which the sensor is located. Such devices may be constructed from conventional integrated circuits and typically are highly accurate and linear over wide temperature ranges. The devices, however, when coupled to provide the temperature indicating voltage output, internally dissipate heat resulting in a transient error for a period of several minutes. This transient error prevents the sensor from attaining a steady-state output within certain tolerances until the expiration of that time. Such lengthy times limit the applications in which the sensors may be utilized.
By way of illustration, temperature sensors are used in many systems in which the reaction time must be very short, sometimes on the order of seconds. In many guidance systems, for example, the reaction time of the system must be sufficient to operate and guide a vehicle or projectile on short notice and for short periods of time. In inertial guidance systems in particular, there is a requirement that the internal temperature of the guidance system be monitored in order to allow calculation of compensation signals for modification of scale factors used in the guidance system. If the guidance system is to only be operable for several seconds, or less than a couple of minutes, the transient error introduced by heat dissipation in conventional temperature sensors prevents accurate temperature signal outputs during guidance system operation.
As a result of the above, guidance systems which employ such temperature sensors cannot be used in situations where the temperature measurements must be made within certain tolerances and within time periods less than those required to achieve a steady-state output. Alternatively, complex and costly circuits must be used to predict the transient error caused by the internal temperature rise in the sensor so that an accurate representation of the temperature is provided for use by the guidance system. In either case, there is no simplified and inexpensive technique available to obtain accurate temperature sensing with fast response times, low cost, and easy implementation with control circuits.
Accordingly, the present invention has been developed to overcome the specific shortcomings of the above known and similar techniques, and to provide an improved temperature sensing system with improved response time and operable over wide temperature ranges.